Underfill process for flip-chip device

ABSTRACT

The present invention relates to a method of packaging a microelectronic device that, in one embodiment, uses a vacuum-assisted underfill process. One embodiment of the method uses a curing process with a tacky film disposed over the device to prevent wicking of the underfill material after the underfill material is in place. One embodiment of the method uses a curing process that utilizes a non-tacky tacky film with a curing process to prevent wicking of the underfill material after the underfill material is in place.

RELATED APPLICATIONS

[0001] The application is a divisional of U.S. patent application Ser.No. 10/032,115, filed Dec. 21, 2001, which is incorporated herein byreference.

FIELD OF THE INVENTION

[0002] The present invention relates to microelectronic devicepackaging. More particularly, the present invention relates to underfillpackaging of a flip-chip package. In particular, the present inventionrelates to a vacuum-assisted underfill process.

BACKGROUND OF THE INVENTION DESCRIPTION OF RELATED ART

[0003] As the process of miniaturization progresses, chip packaging isalso required to be miniaturized. This requirement has resulted inchip-scale packaging, wherein the ultimate goal is to have the chip andthe chip package be virtually the same size.

[0004] A chip package usually includes a mounting substrate and asemiconductor chip or die that is located on or in the mountingsubstrate. One class of chip packaging includes semiconductor chips thatare produced with C4 (controlled collapse chip connect) solderconnections, on an active surface thereof, for purposes of electricallycontacting the integrated circuit on the active surface of the chip tocontact pads on the mounting substrate. The term active surface of asemiconductor chip or die, as used herein, means the surface of the chipor die which carries integrated circuitry. The term back surface, asused herein, means a side of the semiconductor chip or die that isopposite and parallel planar with the active surface.

[0005] During chip packaging, an epoxy is introduced under capillaryaction into a space between the die and the mounting substrate and iscured thereafter. The epoxy acts to bond the die to the mountingsubstrate and to protect the C4 solder connections during thetemperature cycling it will experience during the product's lifetime.

[0006] As depicted in FIG. 1A and FIG. 1B, a chip package 10 includes adie 12, a mounting substrate 14, an electrical connection 16 such as aC4 bump, and an underfill material 18 that has been inserted between thedie 12 and the mounting substrate 14 by capillary action. FIG. 1Adepicts a nonuniform profile 20 and 21 of the underfill material 18including a fillet portion 22 and 23, and an interstitial portion 24that is sandwiched between the die 12 and the mounting substrate 14. Itis noted in FIG. 1B that there is a tongue 25 of epoxy underfillmaterial 18 on one side thereof. Accordingly, the fillet portion 22 and23 that is depicted at profiles 20 and 21 in FIG. 1A exhibits anasymmetrical footprint upon the mounting substrate 14 as depicted inFIG. 1B. Although this tongue 25 of epoxy underfill material 18 may beof no consequence in some prior art embodiments, the pressure tominiaturize and to get even tighter bump pitch and chip-to-package gapheight causes the presence of the tongue 25 to be undesirable.

[0007] One possible solution that is used in production is depicted inFIG. 2A and FIG. 2B. Processing is accomplished by directing a moldpress 26 against a die 12 and a mounting substrate 14. Between the moldpress 26 and the die 12 and mounting substrate 14, an adhesion-resistantfilm 28 is placed that is stretched and held while an underfill materialfeed tube 30 and a vent or vacuum tube 32 are used to flow underfillmaterial 18 between die 12 and mounting substrate 14. After theunderfill material 18 has been properly flowed therebetween to formuniform fillet portions 22 and the interstitial portion 24, the adhesionresistant film 28 and the mold press 26 are removed as depicted in FIG.2B. As the adhesion resistant film 28 and the mold press 26 are removed,some wicking action between the adhesion resistant film 28 and theunderfill material 18 forms an uneven surface 34 (depicted in anarbitrary shape and surface roughness) that often must be smoothed aftercuring. Additionally, and more serious to process yield, some wickspillage 36 forms on the back surface 38 of die 12 that must be removed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] In order that the manner in which embodiments of the presentinvention are obtained, a more particular description of the inventionbriefly described above will be rendered by reference to specificembodiments thereof which are illustrated in the appended drawings.Understanding that these drawings depict only typical embodiments of theinvention that are not necessarily drawn to scale and are not thereforeto be considered to be limiting of its scope, the invention will bedescribed and explained with additional specificity and detail throughthe use of the accompanying drawings in which:

[0009]FIG. 1A is a cross section of a prior art chip package;

[0010]FIG. 1B is a top plan view of the chip package depicted in FIG.1A;

[0011]FIG. 2A is a cross section of a prior art chip package duringprocessing;

[0012]FIG. 2B is a cross section of the chip package depicted in FIG. 2after further processing;

[0013]FIG. 3A is a cross section of a chip package during processingaccording to an embodiment;

[0014]FIG. 3B is a cross section of the chip package depicted in FIG. 3Aafter further processing;

[0015]FIG. 3C is a cross section of the chip package depicted in FIG. 3Aafter further processing;

[0016]FIG. 4A is a cross section of a chip package during processingaccording to an embodiment;

[0017]FIG. 4B is a cross section of the chip package depicted in FIG. 4Aafter further processing;

[0018]FIG. 5 is a top plan view of the chip package that is achievedaccording to an embodiment; and

[0019]FIG. 6 is a process flow block diagram of the inventive process.

DETAILED DESCRIPTION OF THE INVENTION

[0020] An embodiment of the present invention relates to a chippackaging process. A semiconductor chip, a semiconductor package, amethod of assembling a semiconductor package, and a method of producinga semiconductor chip are also described as embodiments. One embodimentrelates to a method of forming a chip package that allows underfillmaterial to be flowed to the chip assembly with no wick spillage ontothe back side of the die.

[0021] The following description includes terms, such as upper, lower,first, second, etc. that are used for descriptive purposes only and arenot to be construed as limiting. The embodiments of a device or articleof the present invention described herein can be manufactured, used, orshipped in a number of positions and orientations. The term “substrate”generally refers to the physical object that is the basic workpiece thatis transformed by various process operations into the desired article. Asubstrate may be made of silica glass or the like, or it may be made ofplastic. A substrate may also be referred to as a wafer. Wafers may bemade of semiconducting, non-semiconducting, or combinations ofsemiconducting and non-semiconducting materials.

[0022] Reference will now be made to the drawings wherein likestructures will be provided with like reference designations. In orderto show the structures of the present invention most clearly, thedrawings included herein are diagrammatic representations of inventivearticles. Thus, the actual appearance of the fabricated structures, forexample in a photomicrograph, may appear different while stillincorporating the essential structures of the present invention.Moreover, the drawings show only the structures necessary to understandthe present invention. Additional structures known in the art have notbeen included to maintain the clarity of the drawings.

[0023]FIG. 3A illustrates a process of underfilling a die according toan embodiment. In a cross-sectional view, FIG. 3A illustrates aflip-chip assembly 110 during underfill processing. The flip-chipassembly 110 includes a semiconductor die 112, according to oneembodiment of the invention, that has a back surface 114 and an activesurface 116. In one embodiment, the semiconductor die 112 is from about4 mils thick to about 50 mils thick.

[0024] Upon the active surface 116, the semiconductor die 112 includes aplurality of C4 solder connections 118 thereon. The solder connections118 may be substituted by solder columns, gold solder connections, orany other connecting structure that is capable of providing electricalinterconnect between the semiconductor die 112 and a host device, suchas a mounting substrate 120, motherboard, or the like. FIG. 3A alsoillustrates a plurality of electrical contact pads 122 thereon. Thesemiconductor die 112 is located on the mounting substrate 120 so thatthe C4 solder connections 118 on the active surface 116 of thesemiconductor die 112 electrically contact the electrical contact pads122.

[0025] Mechanical and electrical connection between the semiconductordie 112 and the mounting substrate 120 is achieved by passing theflip-chip assembly 110 through a reflow oven using a defined reflowprofile for the selected solder material.

[0026]FIG. 3A also illustrates the presence of an underfill material 124that has been applied in a space provided between the semiconductor die112 and the mounting substrate 120. The underfill material 124 providesprotection for the C4 solder connections 118 during temperature cycles.In one embodiment, the underfill material 124 is a substance which has acoefficient of thermal expansion which is similar to the coefficient ofthermal expansion of the C4 solder connections 118. The underfillmaterial 124 also acts to bond semiconductor die 112 to mountingsubstrate 120. In one embodiment, the underfill material 124 containssilicon dioxide particles in order to provide the underfill material 124with a coefficient of thermal expansion which closely matches thecoefficient of thermal expansion of the C4 solder connections 118. Inone embodiment, the silicon dioxide particles are substantiallyspherical.

[0027] The underfill material 124 is introduced on a side of thesemiconductor die 112 by a feed conduit 126 and a gas outlet conduit128. The process of getting the underfill material 124 to flow into thespace provided between the semiconductor die 112 and the mountingsubstrate 120 includes capillary action, pressure feeding through feedconduit 126, and pulling a vacuum through gas outlet conduit 128. It isnoted that one, two, or three of these actions may be combined to getthe underfill material 124 to properly flow. Underfill material thatflows by any or all of these actions is known in the art.

[0028] In a general embodiment, the film 130 is depicted in FIG. 3A ashaving been stretched over the flip-chip assembly 110 and a mold press132 is depicted as rendering a cross-sectional profile to film 130, andconsequently to the underfill material 124. Of underfill material 124,it may be referred to as a fillet portion 134 and an interstitialportion 136 between the die 112 and the mounting substrate 120.

[0029] In a first specific embodiment class, a method of forming apackage includes the use of a tacky film 130 that achieves a releaseunder thermal processing conditions. The method includes placing thetacky film 130 against the flip-chip assembly 110, and particularlystretching it over the semiconductor die 112 and onto the mountingsubstrate 120. The form that the tacky film 130 takes is influenced bythe shape of the mold press 132 that seals the tacky film 130 againstthe mounting substrate 120. After sealing the tacky film 130 against themounting substrate 120, underfilling of the die is accomplished with theunderfill material 124. Thereafter, the mold press 132 is withdrawn, andthe tacky film 130 holds the underfill material in place and retains itscross-sectional profile imparted to it by the mold press 132 as depictedin FIG. 3B.

[0030] After removing the mold press 132, the flip-chip assembly 110 isplaced in a heating environment to cure the underfill material 124. Atsome time after beginning the curing of the underfill material 124, thetacky film 130 releases due to the heat effect on the tacky substance,and the tacky film 130 is removed. Tacky film materials such as No.3195VS film from Lockwood Industries, of Canoga Park, Calif., arecurrently used for heat-releasable applications and are known in theart.

[0031] Conditions that cause the tacky film 130 to release from theflip-chip assembly 110 depend upon the specific tacky film. Variouscuring schemes may be used. In one embodiment, a two-stage heat curingscheme is used. According to this embodiment, the method proceeds to atime after beginning curing the underfill material 124. Heating of thepackage is carried out in a curing oven under conditions to cause thetacky film 130 to release from the flip-chip assembly 110. This heatingscheme includes a first temperature ramp from the ambient afterunderfilling, to a temperature range from about 100° C. to about 140° C.Next, a temperature hold is maintained at a temperature in this range.The temperature hold may be from about 10 seconds to about 30 minutes.The first temperature hold achieves an initial cure of the underfillmaterial 124. Thereafter, a second temperature ramp is accomplished toget the tacky film 130 to release from the flip-chip assembly 110. Thesecond temperature ramp is carried out to a temperature range from about140° C. to about 260° C. After achieving a selected temperature in thisrange, it may be held from about 10 seconds to about 30 minutes.However, in one embodiment, no substantial hold time is required as thetacky film 130 releases upon achieving a selected tacky film 130releasing temperature. Thereafter, ambient cooling of flip-chip assembly110 may be done. Removal of the tacky film 130 may precede or follow theambient cooling.

[0032] According to the first specific embodiment class, anotherembodiment uses a single temperature-ramp curing scheme. In thisembodiment, a linear continuous curing oven is set to a selectedtemperature and flip-chip assembly 110 heats to desired temperatures asit passes through the oven. In one embodiment, the temperature rampbegins at the post-underfill ambient, and ends in a range from about140° C. to about 240° C. The oven time ranges from about 10 seconds toabout 90 minutes. Thereafter, ambient cooling of flip-chip assembly 110may be done. Removal of the tacky film 130 may precede or follow theambient cooling.

[0033] As depicted in FIG. 3C, flip-chip assembly 110 has been heatcured according to an embodiment. It is noted that the cured underfillmaterial 124 includes the fillet portion 134 and the interstitialportion 136 that is between the die 112 and the mounting substrate 120.It is further noted that the fillet portion 134 includes a surfaceroughness 138 and pattern that is characteristic of the surfaceroughness and pattern that was impressed into the fillet portion 134 bythe tacky film 130. Further, it is noted that the wherein the filletportion 134 exhibits a concave curvilinear cross-sectional profile alongits surface roughness 138. This optional concave curvilinearcross-sectional profile is caused by contraction of the underfillmaterial 124 during the curing process according to an embodiment.

[0034] In a second specific method embodiment class, a non-tacky film isused as depicted in FIG. 4A. In a cross-sectional view, FIG. 4Aillustrates a flip-chip assembly 210 during underfill processing. Theflip-chip assembly 210 includes a semiconductor die 212, according toone embodiment of the invention, that has a back surface 214 and anactive surface 216 as set forth herein. In one embodiment, the die 212is from about 4 mils thick to about 50 mils thick.

[0035] Upon the active surface 216, the semiconductor die 212 includes aplurality of C4 solder connections 218 thereon similar to what isdepicted in FIG. 3A. FIG. 4A also illustrates a plurality of electricalcontact pads 222 thereon.

[0036]FIG. 4A also illustrates the presence of an underfill material224. The underfill material 224 is introduced on a side of thesemiconductor die 212 by a feed conduit (not pictured) and a gas outletconduit (not pictured) that are similar to the embodiment depicted inFIG. 3A. A non-tacky film 230 is depicted in FIG. 4A as having beenstretched over the flip-chip assembly 210 and a mold press 232 isdepicted as rendering a cross-sectional profile to non-tacky film 230,and consequently to the underfill material 224. Of underfill material224, it includes a fillet portion 234 and an interstitial portion 236between the die 212 and the mounting substrate 220.

[0037] The method includes placing the non-tacky film 230 against theflip-chip assembly 210, and stretching it over the semiconductor die 212and onto the mounting substrate 220. The form that the non-tacky film230 takes is influenced by the shape of the mold press 232 that holdsthe non-tacky film 230 against the mounting substrate 220. Aftersecurely holding the non-tacky film 230 against the mounting substrate220, underfilling of the die 212 is accomplished with the underfillmaterial 224.

[0038] The mold press 232 has a heater element 238 (depictedschematically). In one embodiment, the heater element 238 acts to cure aportion of the underfill material 224 that is in contact with thenon-tacky film 230. FIG. 4B depicts the flip-chip assembly 210 after thenon-tacky film 230 has been removed, but before a completed cure of theunderfill material 224 has been accomplished. A conductive heat transferprocess has been carried out between the mold press 232 (FIG. 4A) by itsheater element 238 (FIG. 4A), and the underfill material 224 ispartially cured, gelled, and solidified.

[0039] After removing the mold press 232 (FIG. 4A) and the non-tackyfilm 230 (FIG. 4A), further processing is carried out to cure the bulkof the underfill material 224. Based on the underfill material andheating approach, there may or may not be a characteristic grain orsolidification morphology 240 as depicted in FIG. 4B. In an embodimentafter removing the mold press 232 and the non-tacky film 230, curing theunderfill material that is between the die and the mounting substrate,is carried out by placing the package into a curing oven.

[0040] In another embodiment, the mold press 232 remains in place duringthe curing process. In one variant of this embodiment, the mold press232 acts as the entire heat source for curing. In another variant ofthis embodiment, the mold press 232 is assisted in the curing process byanother heat source such as a curing oven as set forth herein.

[0041] In any event, oven curing according to this embodiment entails atwo-stage ramp-and-hold process, or a single-ramp process as set forthherein. Similar to the embodiment depicted in FIG. 3C, the embodimentdepicted in FIG. 4B includes a cured underfill material 224, includingthe fillet portion 234, and an interstitial portion 224 between the die212 and the mounting substrate 220. The concave curvilinearcross-sectional profile is caused by contraction of the underfillmaterial 224 during the curing process according to an embodiment.

[0042] Various curing schemes may be used. In one embodiment, atwo-stage heat curing scheme is used. According to this embodiment, themethod accordingly proceeds to a time after beginning curing the bulk ofthe underfill material 224. This heating scheme includes a firsttemperature ramp to a temperature range from about 100° C. to about 180°C. Next, a temperature hold is maintained at a temperature in thisrange. The temperature hold may be from about 10 seconds to about 90minutes. The first temperature hold achieves a cure of the bulk of theunderfill material 224. Thereafter, a second temperature ramp isaccomplished. The second temperature ramp is carried out to atemperature range from about 140° C. to about 260° C. After achieving aselected temperature in this range, it may be held from about 10 secondsto about 30 minutes. However, in one embodiment, no substantial holdtime is required as the non-tacky film 230 may be removed at any timeafter the gelling of the underfill material 224. Thereafter, ambientcooling of the flip-chip assembly 210 may be done. As set forth herein,removal of the non-tacky film 230 may precede or follow the ambientcooling.

[0043] In another embodiment, a single ramp-ramp curing scheme is used.In this embodiment, a linear continuous curing oven is set to a selectedtemperature and flip-chip assembly 210 heats as it passes through theoven. In one embodiment, the single step temperature ramp is in a rangefrom about 140° C. to about 240° C. Thereafter, ambient cooling offlip-chip assembly 210 may be done. As set forth herein, removal of thenon-tacky film 230 may precede or follow the ambient cooling.

[0044]FIG. 5 illustrates a top plan view of an embodiment that isachievable by either of the processes depicted in FIGS. 3 and 4. Aflip-chip assembly 310 includes a semiconductor die 312, a mountingsubstrate 314, and the fillet portion 316 of an underfill material.Unlike the prior art structures, it is noted that the fillet portion 316is determined by the press mold an in most cases exhibits a symmetricalrectilinear footprint 318 on the mounting substrate 314. Further, thefillet portion 316 fillet portion includes a surface roughness andpattern that is characteristic of the imprint that an interstitial filmsurface roughness and pattern leaves according to the embodiments setforth herein.

[0045]FIG. 6 illustrates a process flow embodiment 600. In a firstprocess flow, a film is placed 610 against a flip-chip assembly. Thefilm may be a tacky film or a non-tacky film as set forth herein. Theflip-chip assembly includes a die, an electrical connection, and amounting substrate. Next, the die is underfilled 620 with underfillmaterial by any method set forth herein. Next, curing 630 of theunderfill material is carried out, but at some time after beginningcuring 630 the underfill material, the film is removed 640. Removal 640may be done according to the sticky-film process embodiments or thenon-sticky film embodiments as set forth herein.

[0046] It will be readily understood to those skilled in the art thatvarious other changes in the details, material, and arrangements of theparts and method stages which have been described and illustrated inorder to explain the nature of this invention may be made withoutdeparting from the principles and scope of the invention as expressed inthe subjoined claims.

What is claimed is:
 1. A method of forming a package, comprising:placing a film against a flip-chip assembly, wherein the flip-chipassembly includes a die, an electrical connection, and a mountingsubstrate; underfilling the die with underfill material; curing theunderfill material; and after beginning curing the underfill material,removing the film.
 2. The method according to claim 1, wherein the filmincludes a tacky film.
 3. The method according to claim 1, wherein thefilm includes a tacky film, and wherein curing the underfill material iscarried out under heat that causes the tacky film to release from theflip-chip assembly.
 4. The method according to claim 1, wherein afterbeginning curing the underfill material and removing the film, curingincludes: curing the underfill material that is in contact with thefilm; removing the film; and thereafter curing the underfill materialthat is between the die and the mounting substrate.
 5. The methodaccording to claim 1, wherein after beginning curing the underfillmaterial and removing the film, curing includes: curing the underfillmaterial that is in contact with the film by conductive heat transferfrom a mold press; removing the film; and thereafter curing theunderfill material that is between the die and the mounting substrate byplacing the package into a curing oven.
 6. The method according to claim1, wherein after beginning curing the underfill material and removingthe film, curing includes: heating the package in a curing oven underconditions to cause the tacky film to release from the flip-chipassembly.
 7. The method according to claim 1, wherein after beginningcuring the underfill material and removing the film, curing includes:heating the package in a curing oven under conditions to cause the tackyfilm to release from the flip-chip assembly, wherein heating includes afirst temperature ramp to a temperature range from about 100° C. toabout 180° C., a temperature hold at a temperature in this range, asecond temperature ramp to a temperature range from about 140° C. toabout 260° C., and cooling.
 8. The method according to claim 1, whereinafter beginning curing the underfill material and removing the film,curing includes: heating the package in a curing oven under conditionsto cause the tacky film to release from the flip-chip assembly, whereinheating includes a single step temperature ramp to a temperature in arange from about 140° C. to about 240° C.; and cooling.
 9. The methodaccording to claim 1, wherein the underfill material has a viscositythat causes it to draw between the die and the mounting substratewithout the assistance of a pressure differential.
 10. The methodaccording to claim 1, wherein the underfill material has a viscositythat causes it to draw between the die and the mounting substrate,further including: flowing the underfill material from a first edge ofthe die to an opposite, second edge of the die by a pressuredifferential.
 11. A method of forming a package, comprising: stretchinga flexible film over die that is mounted on a mounting substrate to sealthe flexible film thereupon; flowing underfill material between the dieand the mounting substrate with a source and a vent; heating theunderfill material to a first curing temperature; and after reaching thefirst curing temperature, removing the flexible film.
 12. The methodaccording to claim 11, wherein the film is selected from a non-tackyfilm and a tacky film.
 13. The method according to claim 11, wherein thefilm includes a tacky film, and wherein heating the underfill materialto a first curing temperature is carried out to cause the underfillmaterial to cure, and wherein the first curing temperature is reached toa temperature range from about 100° C. to about 180° C.; and wherein thesecond curing temperature causes the tacky film to release from the dieand mounting substrate, and wherein the second curing temperature isreached to a temperature range from 140° C. to about 260° C.
 14. Themethod according to claim 11, wherein the film is a non-tacky film andwherein after heating the underfill material to a first curingtemperature and removing the film, curing includes: gelling theunderfill material that is in contact with the film; removing the film;and the process further including: curing the underfill material that isbetween the die and the mounting substrate.
 15. The method according toclaim 11, wherein heating the underfill material to a first curingtemperature includes: heating along a first temperature ramp to a firsttemperature range from about 100° C. to about 180° C.; and furtherincluding: holding the first temperature; heating along a second ramp toa temperature range from about 140° C. to about 260°0 C.; and cooling.16. The method according to claim 11, wherein the underfill material hasa viscosity that causes it to draw between the die and the mountingsubstrate, further including: flowing the underfill material from afirst edge of the die to an opposite, second edge of the die by apressure differential.
 17. A chip package comprising: a die; a mountingsubstrate; an electrical connection disposed between the mountingsubstrate and the die; a cured underfill material including a filletportion, and an interstitial portion disposed between the die and themounting substrate, wherein the fillet portion includes a surfaceroughness and pattern that is characteristic of an interstitial filmsurface roughness and pattern.
 18. The chip package according to claim17, wherein the interstitial film surface roughness and pattern isderived from a film selected from a tacky film and a non-tacky film. 19.The chip package according to claim 17, wherein the fillet portionexhibits a single-stage solidification profile in cross section.
 20. Thechip package according to claim 17, wherein the fillet portion exhibitsa symmetrical rectilinear or other controllable footprint on themounting substrate.
 21. The chip package according to claim 17, whereinthe fillet portion exhibits a concave curvilinear cross-sectionalprofile.
 22. The chip package according to claim 17, wherein theelectrical connection disposed between the mounting substrate and thedie is selected from a ball grid array, a collapsed ball grid array, anda pin grid array.
 23. A chip-packaging process system comprising: a die;a mounting substrate; an electrical connection disposed between themounting substrate and the die; a tacky film that is disposed over thedie and stretched onto the mounting substrate; a mold press that gives ashape to the film; an underfill material disposed between the die andthe mounting substrate; and an underfill inlet and outlet system thatcommunicates through the film.
 24. The chip-packaging process systemaccording to claim 23, wherein the underfill inlet and outlet systemincludes an underfill conduit and a vent.
 25. The chip-packaging processsystem according to claim 23, wherein the underfill material includes afillet shape disposed between the die and the mounting substrate, andwherein the a mold press that gives shape to the film includes a heaterelement disposed at the fillet.
 26. The chip-packaging process systemaccording to claim 23, further including: a first heating source forramping the temperature of the underfill material to a first cure state;and a second heating source for causing the tacky film to release fromthe die, the fillet, and the mounting substrate.